At least 127 test-takers in a Chinese province hired other people to take the country’s all-important college entrance exam on their behalf, the provincial college admission office said.

The Higher Education Admission Office of the central Henan province promised a full investigation into the scam after state broadcaster China Central Television ran an expose piece about it on Tuesday.

Education authorities have imposed increasingly strict rules to guard against cheating during the exam, which is called the “gaokao” and has the reputation of being China’s level playing field for academic advancement. Cheating is not unheard of, especially using electronic gadgets, but hiring of surrogate test-takers has so far been rare.

Almost all Chinese high school graduates must take the exam, and their scores are the key criterion for what tier of university they can enter.

Competition in Henan province is especially intense because it has a larger student population and fewer allocated slots in Chinese universities as compared with many other provinces.